Supramolecular Sensing of 2,4,6-Trinitrophenol by a Tetrapyrenyl Conjugate of Calix[4]arene: Applicability in Solution, in Solid State, and on the Strips of Cellulose and Silica Gel and the Image Processing by a Cellular Phone

Abstract

A calix[4]arene conjugate possessing a tetrapyrenyl moiety at its upper rim (R) is designed as a receptor for sensing trinitrophenol (TNP). To understand the role of the calix[4]arene platform and that of pyrenyl moieties in R, two other control molecules were synthesized. These are as follows: the one possessing a tetraphenyl moiety in place of tetrapyrenyl (R1) and the other one is a p-pyrenyl-hydroxy benzene (R2) that is devoid of the calix[4]arene platform. The R shows high sensitivity toward TNP in tetrahydrofuran (THF) over eleven other nitroaromatic compounds (NACs) studied by exhibiting large fluorescence enhancement and hence is selective to TNP over the other NACs studied. However, the control molecules R1 and R2 showed only marginal fluorescence enhancement, supporting the need of a calixarene platform and the presence of a tetrapyrenyl moiety in the receptor system for the selective sensing of TNP. Further, R1 and R2 are not suitable for sensing, since these exhibit similar fluorescence response over several NACs studied. The binding of TNP by R has been addressed by fluorescence titration and isothermal titration calorimetry. The nature of the complexation of TNP by R has been revealed by the computational calculations, wherein the data showed the entrapment of TNP by two adjacent pyrene moieties via π–π stacking interactions. Such host–guest complexation is expected to restrict the mobility of the pyrene moieties present in R. The reduction of the flexibility of the pyrenyl moieties of R upon TNP binding is evidenced by the 1H NMR spectral study, wherein this acts as an additional evidence for the complexation. In the present study, the sensing of TNP by R has been shown in THF solution, on the surface of silica gel and the cellulose paper to result in lowest detection limits (LODs) of 1.5, 3.5, and 6.5 μM, respectively. Even the solid mixture of R and TNP showed LOD of 2.1 μmol. Since R is expected to show supramolecular aggregation that is dependent on the guest species, the corresponding details were probed by microscopy techniques, using scanning electron microscopy, atomic force microscopy, and transmission electron microscopy methods, and significant changes in the aggregation of R upon interaction with TNP were found. Such aggregation is responsible for the observed fluorescence enhancement. Thus, the tetrapyrenyl calix[4]arene conjugate (R) acts as a sensitive and robust platform for selective detection of TNP from a mixture of nitroaromatic compounds (NACs) wherein the fluorescence intensities can be imaged and managed by a cellular phone.

Supraamphiphilic Systems Based on Metallosurfactant and Calix[4]resorcinol: Self-Assembly and Drug Delivery Potential

“…The use of calixarenes as a macrocyclic component is particularly attractive due to the possibility of modification by various functional groups on both sides of the macrocyclic platform. Moreover, calixarenes are capable of forming complexes with various ions and small organic molecules, which can enter the aromatic cavity of the calixarene framework. − The guest molecules can also be bonded by calixarene substituents located outside the macrocyclic cavity. Sulfonated calix[4]­arenes typically form supraamphiphiles with cationic surfactant molecules due to electrostatic interactions. ,,,− The complexation between the surfactant and the macrocycle in this case leads to a decrease in the critical aggregation concentration compared of the individual components.…”

Adhesion of Grafted-to Polyelectrolyte Brushes Functionalized with Calix[4]resorcinarene and Deposited as a Monolayer

“…Calixarenes [1][2][3][4][5] are bowl-shaped molecules that can be used to form monolayers on surfaces with controlled orientation due to the hydrophilic nature of the hydroxyls on the upper rim, or via chemical functionalization of the upper or lower rim. [6][7][8][9] This capacity for modification also allows additional functionality to be introduced to a surface or solution. 1,3,6,7,[9][10][11] One potential use of this functionalization is to deliver an adhesive to a surface of interest.…”

“…[6][7][8][9] This capacity for modification also allows additional functionality to be introduced to a surface or solution. 1,3,6,7,[9][10][11] One potential use of this functionalization is to deliver an adhesive to a surface of interest. In this work, polyelectrolytes, with a view to switchable adhesion applications, [12][13][14][15][16] were delivered to surfaces utilizing the monolayer capacity of calixarene and its hydroxyl rich rim.…”

“…Calixarenes − are bowl-shaped molecules that can be used to form monolayers on surfaces with controlled orientation due to the hydrophilic nature of the hydroxyls on the upper rim, or via chemical functionalization of the upper or lower rim. − This capacity for modification also allows additional functionality to be introduced to a surface or solution. ,,,,− One potential use of this functionalization is to deliver an adhesive to a surface of interest. In this work, polyelectrolytes, with a view to switchable adhesion applications, − were delivered to surfaces utilizing the monolayer capacity of calixarene and its hydroxyl rich rim.…”

Chemoselective Detection of 2,4,6‐trinitrophenol by Ground State Adduct Formation via Protonation of Quinoline Moiety of Non‐heme Ligands with Structural Evidence

“…[9] A wide number of free ligands such as imidazole derivatives and 4,40-(9,9-dimethylfluorene-2,7-diyl)dibenzoic has shown high sensitivity towards TNP detection. [10] Rao et al have used tetrapyrenyl calix[4]arene conjugate moiety [11] while Das and coworkers have reported newly designed azo-polymer in TNP detection. [12] A hemicyanine dye bearing conjugated 4-(dimethylamino)benzaldehyde based fluorophores are known for its valuable property of sensing TNP.…”